docs: def do_open(self, mode=None):
          """
          Open the current base file with the (original) mode and encoding.
          Return the resulting stream.
  
          Note:  Copied from stdlib.  Added option to override 'mode'
          """
          if mode is None:
              mode = self.mode
  
          with self._alter_umask():
              # noinspection PyArgumentList
              stream = io.open(
                  self.baseFilename, mode=mode, encoding=self.encoding, newline=self.newline)
  
          self._do_chown_and_chmod(self.baseFilename)
  
          return stream